Hylobates moloch

Short phrases consisting of simple hoots and more
complex hoots, among which longer hoots with one or two frequency inflections ("wa-oo",
"wa-oo-wa") are particularly prominent for this species. Short phrases
uttered by males and females. Only one of the males regularly produced bi-phasic
hoots (softer than those of H. agilis) and short trills. Female great call
consisting of a series of accelerated notes; climax not marked by particular frequency
modulation of notes, but by moderately accelerated rhythm of notes becoming slower
again at the end of the great call. Male does not produce coda. Male solo song bouts
and female solo song bouts.

Communal call bout of family group, consisting of adult
pair "Ivanowitch" and "Paula" and their juvenile son (2 year
old), Berlin Zoo, Germany, 30 June 1988.

Female great call from later in the same call bout
as above, adult mated female "Paula", Berlin Zoo, Germany, 30 June 1988.

Disturbance hoots, mated male, 1 Oct. 1998, Dieng Plateau,
Java, Indonesia.
The male hoots at the observer. Hoots like these may occasionally develop into male
solo song bouts. This did not happen on this particular occasion.

Duet song, adult male H. lar and adult female
H. moloch, 30 April 1979, Knie's Kinderzoo, Rapperswil, Switzerland (rec.
Martin Schwarz).
Interestingly, duetting between these two species is possible, although H. moloch
pairs are not known to produce duets.